The present invention relates to a refrigerating apparatus that employs an HFC (hydrofluorocarbon) refrigerant.
Recently, there have been energetically developed refrigerating apparatuses that employ an HFC refrigerant in place of an HCFC (hydrochlorofluorocarbon) refrigerant. As the above-mentioned HFC refrigerant, there are R407C (mixture refrigerant of HFC32, HFC125 and HFC134a), R410A (mixture refrigerant of HFC32 and HFC125) and the like. However, the above-mentioned R407C and R410A refrigerants have high global warming effects although they take no ozone disrupting action, and the refrigerants have the drawback of poor cooling efficiency in a refrigerating apparatus since their coefficients of performance are low.
Accordingly, there is recently proposed a refrigerating apparatus that employs a single substance of R32 (difluoromethane) or an HFC refrigerant that has a principal ingredient of R32. The substance of R32, which has a lower global warming effect than that of the R407C and R410A refrigerant and has a high coefficient of performance, improves the cooling efficiency of the refrigerating apparatus.
However, in the refrigerating apparatus that employs the R32 refrigerant, a temperature when the refrigerant is discharged from a compressor during a compression process becomes about 20xc2x0 C. higher than a temperature when the R407C refrigerant is employed, and therefore, the temperature of the compressor rises. On the other hand, an insulating film owned by a built-in motor of the compressor is made of polyethylene terephthalate (hereinafter referred to as PET) and polyethylene naphthalate (hereinafter referred to as PEN), which can easily be processed. However, these substances of PET and PEN have hydrolyzability. Therefore, when the compressor is the type that has a built-in motor, the insulating film is rapidly deteriorated as a consequence of the promotion of hydrolysis due to moisture in the refrigeration circuit by the high temperature of the compressor that employs R32. This consequently causes a problem that the insulation of the motor is destroyed and the compressor breaks down. The present inventor discovered the fact that the aforementioned problem exists when the refrigerant having a principal ingredient of R32 and the compressor having the built-in motor are employed.
This trouble does not occur when PPS (polyphenylene sulfide) or PEEK (polyether ether ketone), which do not cause hydrolysis and have a high heat-proof temperature, are employed for the insulating film, whereas there occurs the problems of cost increase and degradation of productivity due to hardness.
Accordingly, the object of the present invention is to provide a refrigerating apparatus, in which the insulating film of a compressor motor is inexpensive and has good processability without causing hydrolysis even when a refrigerant having a principal ingredient of R32 is employed, therefor assuring stable maintenance of its performance.
This object is obtained by a refrigerating apparatus having at least a compressor, a condenser, an expansion mechanism and an evaporator, comprising: a refrigerant having a principal ingredient of R32; and a refrigerating machine oil having hygroscopicity, the compressor including a built-in motor, and the motor having an insulating film made of a polymer resin that includes ester linkages.
According to the above refrigerating apparatus, the refrigerating machine oil has hygroscopicity and absorbs moisture in the refrigeration circuit while circulating through the refrigeration circuit. Therefore, even if the amount of water to be absorbed by the insulating film of the motor is decreased and the refrigerant having the principal ingredient of R32 comes to have an elevated temperature during the compression process to cause the elevated temperature of the compressor, the insulating film is hard to hydrolyze. That is, the insulating film is hard to deteriorate, and therefore, the refrigerating apparatus can stably maintain its performance.
According to a preferred embodiment of a refrigerating apparatus, the refrigerating machine oil is an ether oil.
According to the above refrigerating apparatus, the ether oil is stable with respect to water and does not cause hydrolysis. Therefore, the function of absorbing moisture in the refrigeration circuit is stably maintained. Therefore, the performance of the refrigerating apparatus is stabilized, preventing the deterioration of the insulating film for a long term. Moreover, the innate lubricating function is also stably maintained, and therefore, the performance of the refrigerating apparatus is stabilized.
According to a further preferred embodiment of a refrigerating apparatus, the insulating film of the motor is comprised of polyethylene terephthalate or polyethylene naphthalate.
According to the above refrigerating apparatus, the moisture in the refrigeration circuit is absorbed by the refrigerating machine oil. Therefore, the insulating film that belongs to the motor and is comprised of PET or PEN is hard to hydrolyze even in the compressor at an elevated temperature in spite of its hydrolyzability. That is, the insulating film is hard to deteriorate, and therefore, the breakdown of the compressor is avoided, and the performance of the refrigerating apparatus is stabilized.
According to a further preferred embodiment of a refrigerating apparatus, the refrigerant contains 70 wt % or more of R32.
According to the above refrigerating apparatus, the moisture in the refrigeration circuit is absorbed by the refrigerating machine oil despite that the refrigerant that contains 70 wt % or more of R32 comes to have an elevated temperature in the compressor. Therefore, the insulating film of the motor of the compressor is hard to hydrolyze. That is, the insulating film is hard to deteriorate, and therefore, the breakdown of the compressor is avoided, and the performance of the refrigerating apparatus is stabilized.
According to a further preferred embodiment of a refrigerating apparatus, the refrigerant is substantially comprised of a single substance of R32.
According to the above refrigerating apparatus, the moisture in the refrigeration circuit is absorbed by the refrigerating machine oil despite that the refrigerant that is substantially comprised of the single substance of R32 comes to have an elevated temperature in the compressor. Therefore, the insulating film of the motor of the compressor is hard to hydrolyze. That is, the insulating film is hard to deteriorate, and therefore, the breakdown of the compressor is avoided, and the performance of the refrigerating apparatus is stabilized.
According to a further preferred embodiment of a refrigerating apparatus, the refrigerating machine oil has a saturated moisture amount of 5000 ppm or more at a temperature of 30xc2x0 C. and a relative humidity of 80%.
According to the above refrigerating apparatus, when the refrigerating machine oil has a saturated moisture amount of 5000 ppm or more at a temperature of 30xc2x0 C. and a relative humidity of 80%, according to one experimental example, the tensile strength retention rate of PET or PEN that serves as the insulating film of the built-in motor of the compressor becomes 50% or more. That is, this refrigerating machine oil avoids deterioration of the insulating film by maintaining the strength of the insulating film. Therefore, the breakdown of the compressor is avoided, and the performance of the refrigerating apparatus is stabilized.
According to a further preferred embodiment of a refrigerating apparatus, the refrigerating machine oil is a polyvinyl ether oil.
According to the above refrigerating apparatus, the polyvinyl ether oil, which has hygroscopicity, absorbs the moisture in the refrigeration circuit to avoid the hydrolysis of the insulating film of the built-in motor of the compressor. That is, the breakdown of the compressor is avoided by preventing the deterioration of the insulating film. Moreover, the polyvinyl ether oil, which is stable with respect to water, stably keeps a water absorbing function and a lubricating function. Moreover, the polyvinyl ether oil, which has a miscibility to R32 that serves as a refrigerant, satisfactorily takes the lubricating function effect without causing the inconvenience of two-phase separation or the like. Furthermore, the polyvinyl ether oil, which has good electric insulating property, is suitable for the compressor with the built-in motor. Therefore, by using the polyvinyl ether oil for the refrigerating machine oil, the performance of the refrigerating apparatus is stabilized for a long term.